1. Field of the Invention
The present invention relates generally to a seat belt retractor used with an automotive vehicle, and more particularly to a seat belt retractor provided with a tensionless mechanism preventing the driver or passenger from feeling any tension caused by a spring used for retracting the seat belt even while fastening same.
2. Description of the Prior Art
Tension caused by a retracting spring provided in a seat belt retractor usually results in an unpleasant feeling of pressure on a vehicle occupant's chest when wearing the seat belt. To overcome this problem, a number of seat belt retractors include a mechanism to eliminate is tension.
For example, there exists a tensionless mechanism in which engagement between a buckle and a tongue is detected by a buckle switch to energize a solenoid, so that a pair of unidirectional gears engage with another gear directly fixed to the spool. Since the pair of gears can rotate in only one direction with respect to each other, the tensionless condition can be readily achieved and the belt reeled out freely in the other direction. Further, the tensionless length of the belt is determined by presetting the reeled-out length of the belt when the tongue and buckle are engaged, and it is possible to automatically prevent the belt from being further retracted unless the tensionless length of the seat belt is changed.
In the above prior-art seat belt retractor, since the belt length reeled out when the buckle is engaged the tongue is determined to be the tensionless length, there is more slack than necessary, disadvantageously permitting a secondary collision to occur between the vehicle occupant and the seat belt or the vehicle itself in an automotive vehicle collision.
In addition, it is necessary to allow the driver to lean forward easily while maintaining the preset tensionless length for when the driver returns to the normal sitting position. Furthermore, it should be easy for the seat belt user to reset the tensionless length in order to adjust it according to personal tastes and varying circumstances.